Studies On Seed Morphological Structure And Germination Characteristics Of Three Elytrigia Species

Elytrigia is a kind of perennial sparse rhizomatous herb of Triticeae in Gramineae,which has strong drought resistance,salt tolerance,and disease resistance.It has become an important parent material for distant hybridization of wheat,and an ideal ecological environment construction grass and an important forage resource in northern China.In this experiment,the seeds of Elytrigia elongata,E.intermedia,and E.repens were used as the research materials,and the differences of seed morphology and anatomical structure of three species of Elytrigia were studied by stereomicroscope and paraffin section technology.Through the indoor light incubator artificial simulated stress test,different Na Cl concentration,different PEG-6000 solution concentration,different hormone concentration,and different salt-alkali concentration have respectively developed.The purpose of this study is to reveal the differences of seed morphology and structure characteristics and seed germination characteristics of three species of Elytrigia under the condition of combined treatment and to provide a scientific theoretical basis for their genetic improvement of drought resistance and salt tolerance,and their production and application in barren and salinizied land in the arid and semi-arid regions.The main results were as follows:(1)The seeds of three species of Elytrigia were all navicular,hairy at the top,slightly different in seed color,mainly yellow,earthy yellow,and dark brown,but there were significant differences in the seed length,seed width,and seed thickness(P < 0.05).The seed length showed the law of E.elongata>E.intermedia>E.repens.The seed width and thickness showed the law of E.intermedia > E.elongata > E.repens,the results showed that there was a rule of E.elongata(0.58 g)> E.intermedia(0.45 g)> E.repens(0.32 g).According to the seed anatomical structure,the seed embryos of three species of Elytrigia were lateral type,all of which were located at the seed base,and the endosperm accounts for the majority of them.However,there were significant differences in seed coat thickness,embryo length,radicle length,embryo bud length,and scutellum size(P < 0.05).Among them,the seed coat thickness of E.intermedia was the largest(11.55 ?m),and that of E.elongata was the smallest(9.23 ?m).(2)Under different Na Cl concentrations(0,50,100,150 and 200 mmol/L),the germination rates,germination potential,germination indexes and vigor indexes of the seeds of E.elongata,E.intermedia and E.repens showed a trend of first increasing and then decreasing,which indicated that the low concentration of Na Cl could promote the germination of seeds,while the high concentration could inhibit the germination of seeds.The MDA contents in the seeds of three Elytrigia species increased with the increase of Na Cl concentration,while the POD,SOD and CAT contents increased firstly and then decreased with the increase of Na Cl concentration,reaching the maximum value at 150 mmol/L Na Cl.The salt tolerance ability of three species of Elytrigia according to the comprehensive evaluation results by the membership function method showed that the order of salt tolerance from stronger to weaker was E.elongata>E.intermedia>E.repens.(3)Under different PEG-6000 solution concentrations(0%,5%,10%,15%,and 20%),the germination rates,germination potential,germination indexes,viability indexes,radicle length and germ length of the seeds of three species of Elytrigia showed a downward trend with the increase of PEG concentration.The seed germination rate of ER065(only 20%)was the lowest when treated with a 20% PEG-6000 solution.The MDA contents of three species of Elytrigia seeds increased gradually with the increase of drought treatment concentration,and the activities of POD,SOD,and CAT increased firstly and then decreased.The order of the drought resistance ability from stronger to weaker of three species of Elytrigia was E.intermedia>E.elongata >E.repens.(4)Under different concentrations of GA3(0,500,1000,1500,and 2000 mmol/L),the seed germination rates and germination potential of three species of Elytrigia increased significantly with the increase of GA3 concentration(0-1500 mmol/L).At the concentration of 1500 mmol/L GA3,the seed germination rates reached the maximum values,so about 1500mmol/L GA3 was confirmed as the most suitable concentration for breaking seed dormancy and germination.After treatment of GA3,the seed vigors and POD activities of three species of Elytrigia increased obviously,while the MDA content was decreased,and the IAA and GA3 activities were increased,while the ABA activities were decreased to stimulate seed germination and growth,which promoted the radicle and bud growth of seeds.This fully showed that the increase of exogenous hormones could promote the growth of seeds.It could regulate the content of endogenous hormones and then the germination of seeds.(5)The effects of different concentrations of mixed saline-alkali solutions(0,50,100,150,and 200 mmol/L)on the seed germination characteristics of three species of Elytrigia were different.The seed germination rates and germination potential of 10 germplasm materials of three species of Elytrigia showed a decreasing trend with the increase of the concentration of the mixed saline-alkali solution and were significantly lower than those of the control(0 mmol/L).The seed POD activities of three Elytrigia species reached their peak at 150 mmol/L,in which the POD activity of EE030 was 3.13 times of the control,and the MDA content was 1.82 times of the control at 200 mmol/L solution concentration.According to the comprehensive analysis results,the order of mixed salt-alkali tolerance from stronger to weaker of three species of Elytrigia was E.elongata>E.intermedia >E.repens.In conclusion,the seed morphological and anatomical characteristics of three species of Elytrigia can be used as a reference for the classification of Elytrigia species.E.elongata and E.intermedia seeds have better germination abilities,and their tolerance to drought,and salt tolerance were significantly stronger than that of E.repens,which could provide a scientific theoretical basis for genetic improvement of Elytrigia.